Rocket Launches Into Space, Then Returns to Launch Pad

JLocke

Just saw this and found it interesting. Jeff Bezos' Blue Origin rocket launches capsule into space, then returns and lands upright. It looks like it's coming in too hot and will crash, then a sudden burst of thrust slows it waaay down for final touchdown.

Jeff Bezos' rocket lands safely after space flight

LoopyByteloose

Dr. Hans Zarkov would be greatly pleased if he were alive today.

lardom

The first thing I thought is "What was Elon Musk's reaction?" I saw one headline that said he went "ballistic". They are, right now, probably thinking of each other.
As weird as it may sound, that's more exciting than a heavyweight boxing match.
Mark Cuban and Richard Branson are also competing for the prize.

erco

Now THAT'S a PID algorithm in action on the booster landing. A pinpoint touchdown on the target landing circle. Looks like the booster actually landed more gently than the capsule, other than a high-G rapid deceleration right near the ground. Reminds me of all those Lunar Lander games in the 80's, attempting to land softly while burning the least fuel.

Agreed, it will be fun to watch the Bezos/Musk battle for space.

jones

Competition? Musk is launching to orbit. This goes straight up to 100 km and back down. This is cool, no doubt about it, but they aren't comparable problems.

Duane Degn

jones wrote: »

Competition? Musk is launching to orbit. This goes straight up to 100 km and back down. This is cool, no doubt about it, but they aren't comparable problems.

This was my thought as well.

I think this landing is great, but I agree there's a big difference between "to space" and "in orbit".

erco wrote: »

Agreed, it will be fun to watch the Bezos/Musk battle for space.

I'm also in agreement. It's a lot of fun to see rich people spending money this way.

RDL2004

People have been launching rockets and having them make controlled, verical landings their tail for years. The only difference here is scale. And from the point of view of the first stage booster, it makes little difference if the payload goes into orbit or not.

I personally don't view this as head to head competition, as one is working to help create a functional transportation system, while the other is making a carnival ride.

Duane Degn

RDL2004 wrote: »

And from the point of view of the first stage booster, it makes little difference if the payload goes into orbit or not.

Is this the same size of a booster used for orbital flights? If so, then I mostly agree.

RDL2004

Due to the fact that the SpaceX rockets have to fly a carefully controlled flight path in order to reach the correct orbit, which usually takes them out over the ocean, I'd guess that it's at least an order of magnitude more difficult for them to return for a controlled landing, since they have to locate and land on a tiny barge instead of just somehow finding the ground.

Buck Rogers

Duane Degn wrote: »

RDL2004 wrote: »

And from the point of view of the first stage booster, it makes little difference if the payload goes into orbit or not.

Is this the same size of a booster used for orbital flights? If so, then I mostly agree.

Hello!
According to his (Bezos) plans include it. However they are not flight rated, which means the booster is only traveling to the limits of our atmosphere, and then returns like that. Eventually they will be making plans to participate in the same program as the Space-X program.
---
Erco? What's your robot doing in his yard throwing early snowballs at the passing cars?

lardom

RDL2004 wrote: »

People have been launching rockets and having them make controlled, verical landings their tail for years. The only difference here is scale. And from the point of view of the first stage booster, it makes little difference if the payload goes into orbit or not.

I personally don't view this as head to head competition, as one is working to help create a functional transportation system, while the other is making a carnival ride.

I thought Musk was trying to build a vehical that could supply the ISS. As it is we have to hitch a ride from the Russians. Not an ideal situation.

Dave Hein

lardom wrote: »

RDL2004 wrote: »

People have been launching rockets and having them make controlled, verical landings their tail for years. The only difference here is scale. And from the point of view of the first stage booster, it makes little difference if the payload goes into orbit or not.

I personally don't view this as head to head competition, as one is working to help create a functional transportation system, while the other is making a carnival ride.

I thought Musk was trying to build a vehical that could supply the ISS. As it is we have to hitch a ride from the Russians. Not an ideal situation.

SpaceX has had a few successful unmanned ISS resupply missions. Their last mission a few months ago failed because a strut broken in the second stage. They plan on launching another mission in December.

SpaceX recently won a contract from NASA to ferry astronauts to the ISS around the end of 2017.

erco

Also much to like about SpaceX's VTOL Grasshopper two years prior.

jones

The difference in the focus of the Bezos' vs Musk's programs will be a lot clearer when SpaceX launches a Falcon Heavy. If that's successful, it will be able to lift 53 metric tons to orbit, more than the Space Shuttle or a Delta IV Heavy. It's hard to find numbers like launch weight for New Shepard, but considering that the New Shepard main engine has only 110,000 lbs of thrust, a Falcon Heavy might be able to take a New Shepard with full fuel and put it into orbit without ever lighting the motor on NS. No one can accuse Musk of thinking small.

localroger

It takes ten times the fuel to get to orbital velocity as it does to get to orbital height. So what SpaceX is trying to do on first-stage return is literally an order of magnitude harder than this demonstration.

Dave Hein

The engine used by Blue Origin has a wider throttle range than the engines used by SpaceX. The Blue Origin rocket can hover before landing. SpaceX's rockets cannot. They must fire at precisely the right time so that velocity is almost zero when they reach the ground. The SpaceX booster has to put payloads into orbit, and I believe there is a trade-off between having a wide throttle range versus having high thrust and efficiency. I think SpaceX will achieve a soft landing eventually, but it will be very difficult to make it reliable. I suspect they'll abandon the soft landing idea at some point in the next few years.

jones

Based on this video, that doesn't seem quite right. I'm just guessing, but from this it looks like they have adequate throttle control and can descend with one engine running.

Dave Hein

The throttle range on the Merlin 1D is 70%-100%. Previous versions of the Merlin engine cannot throttle down to 70%. Only one engine is needed on descent because the booster has almost no fuel in it, and fuel makes up most of the weight of the booster at launch. To be able to hover, the booster's weight must fall within the 70%-100% range of a single engine. I'm guessing that the Grasshopper and the FR9 were weighted so that they fell within this range.

My understanding is that the weight of an almost empty booster after a launch is less than the minimum thrust of one engine, which means that it cannot hover. The booster must land using a "hover-slam" method, where the velocity must be decreased to zero at the time it reaches the ground without hovering.

SpaceX is working on a new engine called Raptor, which will have a wider throttle range. The Raptor engine may allow hovering. Of course, hovering requires even more fuel, so there are limits on how long the rocket can hover.

My understanding is that the fuel used for landing is the extra fuel that is used to provide a margin of error for launching. As long as the launch is nominal there will be fuel left over. If the launch required more fuel for a launch due to a mechanical issue there would be nothing left for landing. Adding the capability to hover will require more fuel, reduce the payload weight or reduce the altitude that can be achieved. In the end, it would cost more to hover, and it would reduce the benefit of having a reusable booster.

jones

Thanks for the additional information, Dave. I was assuming that an "F9R" would be configured to mimic a real F9 on its way down but maybe they aren't to that point yet. It's certainly fun to watch those things landing sci-fi style.

RDL2004

Yeah, you can't really compare a test flight such as that to an actual operational flight. When a payload has to be put into orbit every drop of fuel may be needed, which doesn't leave much for playing around with engine throttling experiments.

Landing rockets sci-fi style is still pretty cool.

X PRIZE Cup 2007 - Northrop Grumman Lunar Lander Challenge

Dave Hein

Another thing you'll notice in the test flights is that there is very little wind. Under normal launch conditions there is almost always some wind. SpaceX can launch their rockets in wind as high as 35MPH, though I doubt they ever launch when the wind is that high.

It becomes much more difficult to make a vertical landing when there is wind. Not only must the vertical velocity be close to zero at touchdown, but the horizontal velocity must be zero as well, and the rocket must be vertical while trying to hit a bullseye on the ground. For a rocket to counter the force of the wind using a gimballed engine it must be pointed slightly into the wind. Of course, this means that the rocket is not vertical.

So the only way a rocket can have zero velocity and be vertical at touchdown is for it to fly into the wind with enough velocity so that by the time it goes back to vertical it's horizontal velocity reaches zero. This becomes even harder if the wind is gusty.

jones

Yup, keeping that pole vertical in any wind is what I think would be the worst issue. IIRC they have nitrogen thrusters at the top of the first stage, but even if they still have propellant at touchdown I doubt they're much help against significant wind. Nothing about it is easy, but then if nobody ever tries, it will always be impossible.

lardom

jones wrote: »

Yup, keeping that pole vertical in any wind is what I think would be the worst issue. IIRC they have nitrogen thrusters at the top of the first stage, but even if they still have propellant at touchdown I doubt they're much help against significant wind. Nothing about it is easy, but then if nobody ever tries, it will always be impossible.

This is a generic comment but what I learn from this forum is great. I looked at the yellow flame and thought "hydrogen". You said "nitrogen thrusters". That got me thinking.
I'll research the SpaceX engine design because then I'll want to know "Does the ISS stay within the magnetosphere? "How fast does the ISS travel?"

jones

Don't take my word without checking. I think I read that there are nitrogen (e.g. cold gas, no flame) thrusters at the top of first stage that are used in the flip-over maneuver they do to get the thing pointed back in the general direction of the landing site. IIRC (again, check) that after one of the landing attempts where the stage tipped over, Musk (or someone) referred to the thrusters as not having sufficient thrust to keep the stage upright.

As for the ISS, yes, stays within the magnetosphere, and the ISS travels at the speed anything in its orbit would travel. In round figures, something like 17,000 mph. Maybe someone here knows more about the magnetosphere than I do (which isn't much), but in general the ISS is protected from the worst of cosmic radiation if that's what you're thinking about. There is the South Atlantic Anomaly which is a region where one of the Van Allen belts is lower and anything passing through that, including the ISS, does experience some additional radiation. Anyone up to speed on the details?

lardom

jones, mentioning nitrogen merely piqued my curiosity.
Actually, I would like to see a base set up on the moon, built by robots. I think it would help in communications and make it possible to launch and return from Mars. I hope these guys succeed because it would make a lunar base a plausible goal.

Dave Hein

@jones, I wasn't aware of the cold nitrogen thrusters, but it makes sense. Some kind of thruster is needed to flip the booster over since the only other propulsion is the main engines. Since the main engines can only gimbal by a small angle it would waste fuel to do the flip with them. Cold gas thrusters produce a small amount of thrust, and I suspect that the SpaceX thrusters only produce a few pounds of force.

@lardom, I agree that we need to set up a base on the Moon first. It only takes three days to travel to the Moon, whereas a trip to Mars takes seven months. A Mars trip can only be done every 26 months when it is closest to the Earth. A Moon trip can be done at any time. A lunar mission only requires packing a week's worth of food and other resources. A Mars mission requires packing over a year's worth of food. And then there's the exposure to weightlessness and radiation for an extended period of time.

On top of all of that we still have hope of finding life on Mars. The last thing we'd want to do is have the potential of exposing Mars to Earth-borne bacteria from manned missions until we thoroughly explored it using unmanned equipment.

Dave Hein

SpaceX did it! They just launched a rocket a few minutes ago, and successfully landed the booster on a landing pad at Cape Canaveral.

Go to http://www.spacex.com/webcast/ and advance the video to 32:23.

jones

Well, now we know it isn't impossible. I think the "competition", if there ever was such a thing, is officially over.

jones wrote: »

Nothing about it is easy, but then if nobody ever tries, it will always be impossible.

RDL2004

And it successfully orbited its payload in the process - it wasn't just a sub-orbital stunt.

Check out the neat 9 minute time exposure photo of the launch and return at the beginning of this article.

http://arstechnica.com/science/2015/12/by-making-a-historic-landing-spacex-launches-new-age-of-spaceflight/

W9GFO

It truly was an incredible accomplishment. However, it does bother me a little that it is so frequently being referred to as "orbital". The Falcon first stage is sub-orbital. It is the second stage that achieves orbit. They are separate vehicles. It is not accurate to say that an orbital rocket has returned to land. There is a very, very large difference in velocity between what the first stage reached and orbital velocity.

What is amazing is that they turned around a rocket that was going 3,700 mph, 45 miles high (not in space), a hundred miles downrange* and returned it to land where it started out.

* I don't actually know how far downrange it went but going downrange is what really sets it apart from what Blue Origin did a short time ago.

jones

"Orbital", meaning part of a launcher sending payloads to orbit as opposed to a straight up/straight down elevator poking its nose a bit out of the atmosphere for a look around. It seems pretty descriptive, even if not precisely accurate. What would you have them call it?